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Broadband Intelligent Network Architecture for Multimedia-on


									               UDC 627.395.74: 621.397.2

               Broadband Intelligent Network Architecture
               for Multimedia-on-Demand Service
               VMasaaki Wakamoto                VMitsunori Fukazawa
                                                                 (Manuscript received May 28,1997)

               This paper proposes a broadband ISDN (B-ISDN) oriented intelligent network (IN) ar-
               chitecture for a multimedia-on-demand (MOD) service. It demonstrates that IN archi-
               tecture is effective for MOD service control. Then, this paper proposes an IN call model
               for B-ISDN, which is an essential model for defining an open interface in the IN archi-
               tecture. The proposed call model can be applied not only to MOD service control, but
               to control of more advanced B-ISDN multimedia services. Also, an example of MOD
               service control based on the proposed IN architecture is given.

1.    Introduction                                              architecture is effective for MOD service control.
      Various multimedia services are expected to               A new call model is then proposed. The proposed
be offered following the deployment of broadband                call model can be applied not only to MOD service
ISDN (B-ISDN) technologies such as ATM switch-                  control but to control of the evolution of B-ISDN
ing and optical transmission systems. Multime-                  multimedia services. Lastly, a VOD service with
dia-on-demand (MOD) services, which provide                     commercial messages is described as a control ex-
users with multimedia information on an on-de-                  ample based on the proposed IN architecture.
mand basis, are considered to be especially prac-
tical to implement. Video-on-demand (VOD) ser-                  2.  Basic concepts of MOD service
vices such as movie-on-demand is one of the most                    control
primitive MOD services. Providing MOD servic-                   2.1 Requirements
es rapidly and efficiently requires a new service                    Compared with conventional broadcast ser-
control architecture based on B-ISDN because ex-                vices such as CATV, which has a set programming
isting architectures were developed mainly for the              schedule, an MOD service enables users to inde-
plain old telephone service (POTS) and narrow-                  pendently select and receive multimedia informa-
band ISDN services.                                             tion whenever they like. This requires a service
      This paper proposes a B-ISDN oriented in-                 control function to connect users to the multime-
telligent network (IN) architecture for a multime-              dia information source on an on-demand basis. To
dia-on-demand (MOD) service. In the IN archi-                   support a service control function for a networked
tecture, services are executed by interworking                  MOD service, the following fundamental require-
between a service control node and a switching                  ments must be satisfied:
node. Therefore, function allocation and an inter-              1) Support for evolutionary B-ISDN signaling
face between these nodes should be specified to                      capability
develop the IN architecture. A call model is an                      The service control architecture must allow
essential model for defining such an interface. In              for future, complex multimedia services. Signal-
this paper, the requirements and a general model                ing capability is one of the most important elements
of an MOD service from the service control view-                of service control. B-ISDN signaling is evolution-
point are described. Next, we explain how the IN                ary; that is, the ITU-T standardizes B-ISDN sig-

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M. Wakamoto et al.: Broadband Intelligent Network Architecture for Multimedia-on-Demand Service

naling in stages.1) For example, signaling capabil-                sists of three functions.
ity set 1 (SCS-1) offers specifications for a single                     The user function receives multimedia infor-
point-to-point connection; and the next capability                 mation from the information source function via
set, SCS-2, supports multiconnection and multi-                    the network function. The user function has a
point (or multiparty) connections. Therefore, a ser-               signaling function for communicating with the
vice control architecture must follow B-ISDN sig-                  network and information source functions to re-
naling design standards.                                           quest and control the information (e.g., search and
2) Support for interoperability and equal access                   retrieval). A decoding function is needed to de-
      In a multicarrier, multivendor, and multipro-                code information which is sent in a coded form.
vider environment, every organization provides its                 The user function also provides a human inter-
own functions (i.e., services and resources). To                   face and a temporary information storage for per-
enable users and information providers (IPs) to                    sonal use.
access these functions from anywhere in the net-                         The network function sends multimedia data
work, the functions must be interoperable. Also,                   from the information source to a user by using
in a multiprovider environment, equal access is                    switching and transmission functions. To connect
indispensable. That is, the service control func-                  a user to an information source on a user-demand
tion must give users equal access to every IP.                     basis, a call and connection control function is
3) Support for customization                                       needed to establish and terminate connections
      Customization of MOD services by IPs must                    dynamically. A signaling function is also needed
be made an easy task for IPs. For example, a cer-                  to support call and connection control. The infor-
tain IP may wish to provide a home shopping ser-                   mation source function is distributed (e.g., each
vice by enhancing an already existing MOD ser-                     IP has all of the information source functions and
vice (e.g., a movie-on-demand service). This                       these functions are connected to a network), thus
requires an open interface to the IPs and localiza-                an information source listing and navigation func-
tion of a customized component of the service con-                 tion is needed to enable users to select an infor-
trol function.                                                     mation source (e.g., an IP). When a user requests
                                                                   an MOD service from an information source, a user
2.2 MOD service control model                                      authorization function analyzes whether the user
     Before describing a network architecture that                 is permitted to use the MOD service and access
satisfies the above requirements, we will describe                 the information source. An accounting function
a fundamental MOD service control model which                      calculates user charges based on network account-
abstractly defines the functions required to pro-                  ing data such as the connection holding time and
vide an MOD service. Figure 1 is a diagram of                      information rate.
our MOD service control model. This model con-                           The information source function supports an

                                                      Network                           Information source
                     User             • Transport                                 •   Storage control
                                        (switching & transmission)                •   Signaling
            •   Signaling             • Call & connection control                 •   Coding
            •   Decoding              • Signaling                                 •   Title listing & navigation
            •   Human interface       • User authorization                        •   User authorization
            •   Temporary storage     • Information source listing & navigation   •   Accounting
                                      • Accounting

                                           Fig.1– MOD service control model.

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                           M. Wakamoto et al.: Broadband Intelligent Network Architecture for Multimedia-on-Demand Service

information storage and sends the multimedia in-                       Proprietary                                     Proprietary
                                                                                             Service controller
formation requested by the users. A storage con-                                             (operations system)
trol function supports basic information control                                                         Network management
                                                                                                         interface (e.g., CMIP)
such as search, retrieval, and storing. Users’ re-                 Subscriber
                                                                                                 ATM switching             Multi-
quests and control signals (via the network func-                   access                                                 media
                                                                    network                      system
tion) are processed by a signaling function. A cod-
ing function is needed to compress video infor-                        CMIP: Common management information protocol
mation. A title listing and navigation function en-                                        a) PVC architecture
ables users to select information titles such as
                                                                                 UNI                               UNI
movie titles. When a user requests a certain in-                                 signaling                         signaling
formation title, a user authorization function an-                 Subscriber                                              Multi-
                                                                    access                       ATM switching             media
alyzes whether the user is permitted to access the                  network                      system                    server
information. An accounting function calculates
the user charge based on the information source’s                                    b) Native SVC architecture
accounting data, for example, charges for provid-
ing information.                                                 Session control interface                           Session control interface
                                                                 (e.g., DSM-CC)                                      (e.g., DSM-CC)
                                                                                           Service controller
                                                                                          Proxy signaling agent
3.  Network architecture for an MOD                                                                        UNI signaling
    service                                                        Subscriber                                              Multi-
3.1 Basic concept                                                   access                       ATM switching             media
                                                                    network                      system                    server
     To construct a network for an MOD service
based on the requirements and MOD service con-
                                                                     DSM-CC: Digital storage media - command and control
trol model described in Chapter 2, we first need                                   c) Proxy signaling architecture
to develop a network architecture based on the
model. We should also consider that B-ISDN of-                                                   Service control
                                                                                                 point (SCP)
fers us a good opportunity to introduce new ideas.                                                       IN application protocol (INAP)
In this chapter, some network architecture alter-                                   UNI                        UNI
                                                                   Subscriber       signaling                  signaling Multi-
natives are considered.                                             access                       ATM switching
                                                                    network                      system
      3.1.1 Network architecture                                                                                         server

                                                                                                d) IN architecture
     Figure 2 shows four typical network archi-
tectures.                                                            Fig.2– Network architectures for a MOD service.
     In the PVC architecture, a service controller
incorporating an operations system controls an                         The native SVC architecture is based on the
ATM switching system in a PVC setup manner.                      conventional call setup method; that is, a user
Control interfaces between the service controller                dials an IP’s number. Call processing in an ATM
and a subscriber access network or an IP’s server                switching system then analyzes the call informa-
are separated from the ATM UNI and are propri-                   tion and establishes a connection between the user
etary. For example, these interfaces will be im-                 and an IP. The control interface uses an ATM UNI
plemented by LAN or WAN. An ATM switching                        control plane such as Q.2931 signaling.
system is controlled via a network management                          The proxy signaling architecture is a kind of
interface such as the common management infor-                   SVC architecture and is currently being studied
mation protocol (CMIP).                                          at the ATM Forum.2) Originally, proxy signaling

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M. Wakamoto et al.: Broadband Intelligent Network Architecture for Multimedia-on-Demand Service

is used for terminals and subscriber access net-                equipment cost can be reduced, which is consid-
works such as CATV networks which do not sup-                   ered to be a very important requirement for rapid
port a UNI signaling function. That is, a proxy                 introduction and growth of a VOD service. On
signaling agent (PSA) acts as an agent of termi-                the other hand, current session control interfaces
nals (or access networks) for UNI signaling. PSA                such as DSM-CC are rather specific to video ser-
is located in a service controller. This capability             vices, so the interface should be enhanced or
is applied to a VOD system in the ATM Forum’s                   changed to enable multimedia service control.
specification. The interface between a PSA and                       The IN architecture will flexibly resolve the
terminals (or access networks) is called the ses-               navigation issue. A logical number, for example,
sion control interface; the digital storage media-              the number of a toll-free phone service, which can
command and control (DSM-CC) will typically be                  be provided by the IN architecture, hides the dis-
used for this interface.                                        tribution among centers from the users. Hiding
      In the IN architecture, a service control point           the distribution is also important for equal access.
(SCP) controls an ATM switching system by the                   Moreover, the IN architecture provides a generic
IN application protocol (INAP).3) Interfaces be-                platform for MOD service customization, flexible
tween an ATM switching system and a subscrib-                   accounting, and authorization for a large-scale
er access network or an IP’s server use an ATM                  network.
control plane, as is the case for the native SVC                      Both the proxy signaling architecture and the
architecture.                                                   IN architecture can satisfy the requirements de-
      3.1.2 Considerations                                      scribed in Section 2.1. In this paper, however, we
      The PVC architecture has the advantage that               focus on the IN architecture because of significant
it can be rapidly implemented using existing fa-                issues regarding its development for B-ISDN. In
cilities such as a CATV network and LAN. How-                   the IN architecture, the network function in the
ever, the real-time performance will be rather low              MOD service control model is divided into the ser-
because it uses network management technolo-                    vice control function (SCF) and the service switch-
gies. Moreover, proprietary interfaces based on                 ing function (SSF)/call control function (CCF). The
LANs or WANs will limit network scale. Thus this                MOD service is provided as an IN supplementary
approach is considered to be suitable only for the              service.
initial stage of an MOD service.
      Although the native SVC architecture can                  3.2 Network configuration
simplify the network configuration, the service                       This section describes a network configura-
control flexibility is insufficient. For example, a             tion for an MOD service based on the IN architec-
nationwide IP will have several server centers.                 ture. Because the standardization of B-ISDN sig-
Therefore, user requests should be distributed                  naling capability is being done stepwise, we
automatically to each center according to the traf-             propose a two-step network construction.
fic conditions. In the native SVC architecture, it                   3.2.1 Step 1
is not easy to flexibly implement such an infor-                      As described in Section 2.1, the service con-
mation source listing and navigation function.                  trol architecture must enable evolution and must
      The proxy signaling architecture will resolve             flexibly follow the current stage of B-ISDN sig-
the performance issue of the PVC architecture and               naling capability. The B-ISDN signaling capabil-
improve the information source listing and navi-                ity is one of the most influential factors in the IN
gation function of the native SVC architecture.                 architecture. SCS-1 is sufficient for an initial
Also, because terminals or access networks need                 MOD service such as a movie-on-demand service
not support a UNI signaling function, the user’s                which needs only single point-to-point connections.

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Enhanced MOD services, however, would need                        er’s terminal (e.g., an enhanced set top box or a
more complex connection control for multiconnec-                  personal computer). The service control point
tion support. For example, a home shopping ser-                   (SCP) will control basic call processing (SSF/CCF)
vice would need a video connection for a video cat-               in the ATM switching system and the multimedia
alog and a data connection for an order form. This                servers. For Step 1, the conventional signaling
requires SCS-2, which supports both multiconnec-                  system No. 7 (SS7) network will be used as the
tion and point-to-multipoint connection control.                  signaling network for cost-effectiveness. The net-
Early MOD services are likely to trigger a rapid                  work management system manages each network
introduction of a variety of enhanced MOD ser-                    element via the data communication network,
vices. The IN service control architecture, there-                which supports the X.25 protocol.
fore, needs to be based on SCS-2 even in its first                      3.2.2 Step 2
implementation. However, it must still support                         For Step 2, the network configuration will be
SCS-1 as a subset of SCS-2 for simple point-to-                   more sophisticated. The IN service control sup-
point MOD services.                                               ports connection control that is more complex than
      Figure 3 shows a Step 1 network configura-                  that supported in SCS-2; for example, it supports
tion. In the early stages of the MOD service’s                    control of multipoint-to-point and multipoint-to-
growth, existing CATV networks will be used as                    multipoint connections. Thus more sophisticated
the subscriber access network because of their                    concurrent information reception from multiple
cost-effectiveness. The CATV network is connect-                  servers and multimedia conferencing can be pro-
ed to the ATM switching system via a cable head                   vided as IN supplementary services.
end system. The cable head end system supports                         Figure 4 shows the Step 2 network configu-
B-ISDN UNI signaling termination and converts                     ration. Optical subscriber loops will be widely
ATM cells into an information stream for the                      used, and private networks will be accommodat-
CATV network. The cable head end system also                      ed. The subscriber’s terminals are enhanced (e.g.,
broadcasts conventional CATV programs. Mass                       a workstation and a multimedia conferencing ter-
storage multimedia servers will be connected to                   minal) and support the B-ISDN UNI signaling
the ATM switching system and will send the re-                    termination function. The main differences from
quested multimedia information to the subscrib-                   the network in Step 1 are an ATM signaling net-

                       Network management system

                   Data communication network (X.25)
                                                                              Service control point       Network management system
                                     Service control point

        CATV                                                        RDP
                                         SS7 network               server                       ATM signaling network

                         ATM switching
                         system                                                            ATM switching
                                           ATM                     Private                 system
                                         switching                 network    Gateway                        ATM
  CATV                     SSF/CCF        system                                                           switching
 network                                                                                      SSF/CCF       system
              Cable                                  Multi-
            head end       ATM switch                media                                                              Multi-
             system                                  server       Enhanced                                              media
                                                                  terminals                  ATM switch
Terminal                                                                                                                server

Fig.3– Network configuration for a MOD service (Step 1).          Fig.4– Network configuration for a MOD service (Step 2).

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M. Wakamoto et al.: Broadband Intelligent Network Architecture for Multimedia-on-Demand Service

work and a real-time distributed processing (RDP)               POTS and narrowband ISDN in mind. It is there-
function. The ATM signaling network provides                    fore difficult to directly apply it to B-ISDN ser-
high-speed communications between network                       vice control, which must manage connection types
nodes. The RDP provides network-wide distribu-                  other than point-to-point. Research into enhance-
tion transparency. The RDP is used for dynamic                  ments of the conventional call model has been re-
SCP selection. That is, when a user requests an                 ported.6), 7) These reports discuss only the basic-
IN supplementary service, an SCP supporting the                 concept or enhanced BCSM; however, they give
requested service is selected. If multiple SCPs                 no specifications for the CSM, which must also be
support the requested service, the SCP with the                 enhanced for B-ISDN.
lightest processing load is selected. Ultimately,                     The B-ISDN call model requires the following:
the RDP is used for mobile multimedia personal                  1) Multiparty and asymmetric connection
communication.                                                        After the Step 1 network has matured, the
                                                                number of services accompanied with unidirec-
4.    IN call model for B-ISDN                                  tional and multiparty connection types will in-
     To implement an MOD service as an IN sup-                  crease. Therefore, a call model must be construct-
plementary service, the IN architecture must in-                ed for services using a uniform control method for
corporate B-ISDN capability. However, current                   all connection types. Moreover, the call model
IN research, including standardization activities               must be designed so that the service logic for the
at ITU-T, mainly focuses on service control for                 various connection types is simplified.
POTS and narrowband ISDN services, indicating                   2) Multimedia services
that B-ISDN service control is presently insuffi-                     After the Step 1 network has matured, it is
cient. When developing the IN architecture in-                  also expected that the need for multimedia ser-
corporating B-ISDN capability, a call model is an               vices will increase. For such services, subscribers
essential part of the IN architecture.4), 5) In this            will be assigned multiple virtual channels (VCs).
chapter, we focus on an IN call model for B-ISDN                Thus, a call model must provide flexible VC con-
that will be applied to both the Step 1 and Step 2              trol. This flexible control includes independent
network described in Section 3.2.                               control of each VC and simultaneous control of
                                                                multiple VCs. A call model must also provide con-
4.1 Requirements for the call model                             trol capability for dynamic addition and deletion
      The call model is a fundamental element for               of a connection in a call.
standardizing the interface between the SCF and                 3) Dynamic modification of bearer capability
SSF/CCF. The call model consists of a call seg-                       In an ATM network, which is the most prom-
ment model (CSM) and a basic call state model                   ising network for realizing B-ISDN, a VC is used
(BCSM). The CSM represents the call control in-                 as a logical communication path. Since the bear-
formation abstractly from the SCF viewpoint. The                er capability of a VC can be modified dynamically
BCSM is a CCF basic call processing model of the                for each call, new services are expected to use this
CCF which defines call state transitions points in              feature. The call model should therefore be de-
calls (PICs) and detection points (DPs). The ease               fined to modify a VC’s parameters when IN ser-
with which services and design applications can                 vices are executed.
be developed depends on the flexibility of the call             4) Communication among various terminals
model. It should also be remembered that the call                     and servers
model must follow the migration of B-ISDN sig-                        With the increase in multimedia services,
naling capability from SCS-1 to beyond SCS-2.                   various types of terminals and IP servers will be
      The conventional call model was studied with              connected to B-ISDN. A network should support

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communications among these terminals and serv-                   2)   Information flow between the SCF and SSF/
ers, and the call model should enable establish-                      CCF
ment of any possible interconnection between                          There are two possible schemes for defining
them.                                                            the information flow between the SCF and SSF/
                                                                 CCF when the CCF is enhanced as described
4.2 Basic concept                                                above. The first scheme is to define an interwork-
      Before discussing the call model, we must                  ing relationship only between the SL and the
consider the function arrangement and informa-                   CLCs. The second scheme is to define multi-in-
tion flow between the SCF and SSF/CCF.                           terworking relationships between the SL, CLCs,
1) CCF for B-ISDN                                                and CNCs.
      If a conventional CCF is used, the service                      The first scheme hides detailed information
logic (SL) in the SCF will be very complicated and               about connection control states from the SL.
the information flow between the SCF and SSF/                    Therefore, the SL and the interworking mecha-
CCF will be very large because basic call process-               nism could be simple. On the other hand, for the
ing in the CCF is too simple to handle multiparty                second scheme, the SCF can control the CCF func-
and/or multiconnection services. Therefore, the                  tions in more detail because the SL can also di-
CCF for B-ISDN should be enhanced to enable a                    rectly interwork with the CNCs. We propose
subscriber to set up a multiparty and/or a multi-                a call model based on the first scheme because
connection call and add/drop parties or connec-                  the first scheme is closer to the basic IN purpose
tions during a call.                                             of rapid service development and realization of
      We have determined that the CCF should be                  service customization and because it can be real-
divided into two types of functional modules (call               ized by extending the current IN mechanism.
control modules [CLCs] and connection control                    Figure 5 shows the proposed CCF structure based
modules [CNCs]) according to the SCS-2 B-ISDN                    on the first scheme.
signaling capability. The CLC has call signaling                      We also evaluated the two schemes theoreti-
termination and connection coordination func-                    cally from the service control overhead viewpoint.
tions. The CNCs have switching resource man-                     The evaluation results show that the first scheme
agement functions, bearer signaling termination
functions, and VC management functions. A ba-
sic call is executed by interworking the CLC and
CNC modules.
      As described in Subsection 3.2.1, in the ini-
tial stage of the Step 1 network, SCS-1 will be
sufficient for the initial MOD service, which re-
quires only single point-to-point connection. In                      SSF

this stage, the CLCs will not need to support all                     CCF
the functions needed for SCS-2, and the actual                              CLC                                    CLC
service control will be almost completely handled
by the CNCs. That is, the call model based on
this separated module concept can follow the mi-                            CNC                                    CNC

gration of B-ISDN signaling capability from SCS-
                                                                                  SL: Service logic
1 to beyond SCS-2.                                                                CLC : Call control module
                                                                                  CNC: Connection control module

                                                                 Fig.5– CCF functional modules and interworking relationship.

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M. Wakamoto et al.: Broadband Intelligent Network Architecture for Multimedia-on-Demand Service

reduces the message traffic between the SCF and
SSF/CCF as compared with the second scheme,
especially in multiconnection control. This reduc-
tion effect becomes more notable as the number
of connections to be controlled increases. The rea-
son for this is as follows. In the second scheme,
each CNC corresponds to a specific connection, and
the SL must control multiple CNCs concurrently
to control multiconnection. That is, multiple con-
trol messages from the SCF to SSF/CCF are need-
ed. On the other hand, for the first scheme, the
multiple control orders for connections can be sent
by one message to the CLCs.                                             Fig.6– Graphical representation of CSM.

4.3 Proposed call model
     In this section, we propose an IN call model               example, the VC status, information rate, and
for B-ISDN based on the requirements and basic                  quality of service (QOS) allocated to the VC.
concept described above.                                        2) Connection points (CPs)
      4.3.1 Call segment model (CSM)                                 Only single connection (bidirectional point-
      The CSM represents call control information,              to-point connection) is considered in the current
for example, the connection type, various resource              IN architecture. The meaning of the term “CP” is
attributes (e.g., various VC setup parameters), and             not fully clear because call and connection estab-
relationships among resources (e.g., connectivity               lishment are the same.
relationship and containment relationship). The                      With the separation of CLCs and CNCs in
CSM is independent of SSF/CCF implementation.                   the CCF for B-ISDN, the SL should be able to dis-
      To satisfy the requirement of Section 4.1,                tinguish between connections and calls. A CP is
each connection and party should be identified in               defined as a logical resource which connects legs
the CSM, and their attributes and relationships                 via a connection type. The SL can control each
should be explicitly represented.                               connection separately by indicating the corre-
      The proposed CSM for B-ISDN consists of                   sponding CP; this meets one of the requirements
legs, connection points (CPs), access ports (APs),              described in 4.1 2). A CP is generated for the re-
and a call segment (CS). Figure 6 shows the CSM.                sources (e.g., a speech path and a conference
The figure shows the state in which an IN service               trunk) and the corresponding control functions
request is detected for party A and a correspond-               which are used to establish the connection in the
ing IN service is invoked while the multiparty and              switching system. A CP has attributes such as
multiconnection control function is executed in the             the reservation status of the corresponding re-
CCF as a basic call.                                            source, connection type, and leg information. In
      The CSM components are described below.                   Fig. 6, the symbols used for CP1 and CP2 repre-
1) Legs                                                         sent a conference-type connection and broadcast-
      A leg is a VC allocated to a subscriber or to a           type connection, respectively.
neighboring switching system by the CCF which                   3) Access port (AP)
has the CSM. These VCs are managed by the                            An AP is a newly defined component for en-
CNCs and are controlled by the CLC, which de-                   abling control of each party. One AP is created for
tects the trigger. A leg has several attributes, for            each CLC. Each AP is a logical resource that bun-

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dles all VCs controlled by the CNCs under the CLC                                             or drop party/connections in the active state.
for which the AP was created. A CLC-related AP                                                Because of these enhancements, CCFs can
that detects an IN service request is called the                                         interact with SCFs at B-ISDN-specific DPs dur-
control-AP. When a CLC detects a signal for add-                                         ing basic call processing, and flexible control of
ing or dropping a party, the corresponding process-                                      various B-ISDN services is possible.
ing (e.g., simultaneous setup/release of multiple
VCs) is executed in the CCF containing the CLC.                                          5.    MOD service control example
       4.3.2 Basic call state model (BCSM)                                                    One of the most important issues regarding
     Figure 7 shows a B-ISDN BCSM for an orig-                                           the popularity of VOD services is user fees. VOD
inating party. The enhanced portions of this                                             service charges must be competitive with video
BCSM are summarized as follows:                                                          rental services. One effective method to ensure
1) “O_Establish_Call” and “O_Establish_                                                  that charges are reasonable is to insert a commer-
     Connection” points in calls (PICs) and                                              cial message (CM) into the VOD programs. This
     “O_Only_Call_Established” detection point                                           chapter describes an example VOD service con-
     (DP) have been defined to support the sepa-                                         trol with CMs that is based on the proposed IN
     ration of call control and connection control.                                      call model.
2) DPs detected at “O_Active” PIC except
     “O_Mid_Call” and “O_Disconnect_Call” are                                            5.1 Network configuration
     also added to enable event detection of add                                              In a VOD service with CMs, a CM video is
                                                                                         sent to the subscriber’s terminal during, before, or
                                                                                         after the VOD program, and the CM sponsor pays
   O_Abandon DP
                                                                                         a part of the VOD service charge. Figure 8 shows
                 O_NULL &                                    Exception
                 Authorizing_Origination_Attemp                                          an example network configuration for a VOD ser-
  Origination_Attemp_Authorized DP                                                       vice with CMs that is based on the Step 2 network
                       Collect_Information                                               (the RDP server is omitted for simplicity). The
                                                   Collect_Timeout DP
    Information_Collected DP
                                                   Invalid_Information DP
                      Analyze_Information                                                                 Service control
                                                   O_Call_Establish_Failure DP
                                                                                                           point (SCP)
    Information_Analyzed DP
    O_Call_Establish DP                                   O_Busy DP                                                          information
                                                   O_Connection_Establish_Failure DP                          SLEE            database

    O_Connection_Established DP      O_Mid_Call DP         O_No_Answer DP
                                                                                                                ATM signaling network

                                     O_Mid_Call DP                                                                                         CM video
                                                           O_Only_Call_Established DP                      ATM switching                    server
                                      O_Answer DP
                                       O_Active                                                                                            CM video
O_Disconnect_                                                         O_Mid_Call DP
Call DP                                                                                                        SSF
                                          O_Connection_             O_Party_Deleted DP
                                          Deleted DP                                                                             VOD program
                                     O_Delete_                O_Delete_Party DP          Subscriber’s          CCF
                                     Connection DP                                       terminal
                             O_Connection_             O_Party_Added DP
                             Added DP

                    O_Add_Connection DP O_Add_Party DP
                                                                                                  SLEE: Service logic execution environment
                           : Point in call (PIC)             : Deletion point (DP)

                                                                                                Fig.8– Example network configuration for
   Fig.7– Basic call state model for originating party.                                                VOD service with CM.

FUJITSU Sci. Tech. J.,33,2,(December 1997)                                                                                                       123
M. Wakamoto et al.: Broadband Intelligent Network Architecture for Multimedia-on-Demand Service

user information database manages information                                           then the first one is torn down.
about the users of the service, for example, the us-                                    Method 1) can be achieved with a B-ISDN,
ers’ occupations and interests. This information                                        signaling-capable SCS-1 that is used for the
is used by an SCP to select CM videos which meet                                        initial stage of the Step 1 network. Method
the users’ interests. This method will enhance the                                      2) needs multipoint-to-point connection con-
usefulness of CMs for users and sponsors.                                               trol (i.e., beyond SCS-2) and it makes service
      In the example shown in Fig. 8, the CM vid-                                       control more complex than method 1). How-
eo and VOD programs are in different video serv-                                        ever, from the user’s viewpoint, method 2) can
ers at different locations. Thus two VC connec-                                         make instantaneous changeovers between
tions must be allocated, and these connections                                          the CM video and the VOD program. There-
must be switched when the CM video or VOD pro-                                          fore, we have adopted method 2) based on the
gram ends. To achieve this, there are two meth-                                         Step 2 network for the service control of VOD
ods for VC connection control:                                                          services with CMs.
1) The first VC connection is torn down, then
      the second one is established.                                              5.2 Service control flow
2) The second VC connection is established,                                             Figure 9 shows the IN service control flow

                                                                                                             Video servers
                                                                                                                                    VOD program
                               ATM switching system           Service control point
                                       SSF                             SLP                     User information
  Subscriber’s terminal                                                                                                          CM video
                                       CCF                             SLEE                       database
               VOD service request
               (User ID, Program ID)      Analyze request
                                              VOD service request
                                                                          VOD service logic
                                              (User ID, Program ID)       program invocation
                                                                           User information request
                                                                           (User ID)                   Search user information

                                                                              Response(CM video ID)
                                               Connect request
                                               Connect ACK
                                                                                        CM video request (CM video ID)
                                                            Sending CM video

                                    AP0         LEG1           LEG2         AP1
                          a)     (Terminal)                              (CM server)
                                                                                        Notify near end of CM video
                                               Connect request
                                               Connect ACK

                                                            LEG2         (CM server)
                                    AP0        LEG1
                                 (Terminal)       CP1                      AP2
                                                            LEG3        (VOD server)
                                                                                        Notify end of CM video
                                                                                        VOD program request (Program ID)
                                                                Sending VOD program
                                               Disconnect request
                                               Disconnect ACK

                                    AP0         LEG1           LEG3        AP2
                          c)     (Terminal)                             (VOD server)

                                  Fig.9– Example IN service control flow for VOD service with CM.

124                                                                                                      FUJITSU Sci. Tech. J.,33,2,(December 1997)
                           M. Wakamoto et al.: Broadband Intelligent Network Architecture for Multimedia-on-Demand Service

of a VOD service with CMs that is based on meth-                 6.   Conclusion
od 2). The following is an outline of the service                     We have proposed a broadband IN architec-
control flow:                                                    ture for an MOD service. We have focused on the
1) When a subscriber requests a VOD service                      call model, which is an essential element of the
      with CMs, a request message is sent to the                 IN architecture. The proposed call model can be
      CCF in the ATM switching system. The CCF                   applied not only to MOD service control but to
      detects a trigger and carries out service anal-            control of evolutionary B-ISDN multimedia ser-
      ysis and user authorization. Then, the SSF                 vices. An MOD service, namely a VOD service with
      sends a trigger to the SCP.                                a commercial message, was described as a control
2) Using the service logic program (SLP), the                    example based on the Step 2 network.
      SCP requests the user information database                      We will continue to study issues regarding
      to select a CM video that meets the users’                 the implementation of the proposed architecture,
      interests and then receives the ID of the se-              especially for Step 2. For example, we will study
      lected video.                                              internetworking with a private network (e.g.,
3) The SCP requests the SSF/CCF to establish                     ATM-LAN), real-time distributed processing, and
      a VC connection between the CM video serv-                 an ATM signaling network.
      er and the subscriber terminal.
4) The SCP activates the CM video server and                     References
      specifies the CM video. Then the server starts             1)   Baseline Text for Harmonized Signaling Re-
      sending the CM video. A graphical represen-                     quirements, ITU-T SG11, 1993.
      tation of the CSM in this state is shown in                2)   The ATM Forum Audiovisual Multimedia
      Fig. 9 a).                                                      Services: Video on Demand Implementation
5) When the CM video is nearly finished, the                          Agreement 1.0, The ATM Forum, 1995.
      SCP is notified. Using the SLP, the SCP re-                3)   ITU-T Q.1200 Series Recommendation, ITU-
      quest the SSF/CCF to establish a VC connec-                     T SG11, 1995 .
      tion between the VOD program server and                    4)   Wakamoto, M., Fukazawa, M., Kim, M.W.,
      the subscriber’s terminal. When the connec-                     and Murakami, K.: Intelligent Network Ar-
      tion is established, the SCP is notified. A                     chitecture with Layered Call Model for Mul-
      graphical representation of the CSM in this                     timedia-on-Demand Service. Proc. the XV In-
      state is shown in Fig. 9 b) (LEG 3 is created                   ternational Switching Symposium, 1, 1995,
      and connected to CP 1).                                         pp. 201-205.
6) When the CM video ends, the SCP is noti-                      5)   Wakamoto, M., Fukazawa, M., Kim, M.W.,
      fied. The SCP activates the VOD program                         and Murakami, K.: Phased Network Con-
      server, and the server starts sending the VOD                   struction for Multimedia-on-Demand Service.
      program.                                                        Proc. the 7th International Networking Plan-
7) Using the SLP, the SCP requests the SSF/                           ning Symposium, 1, 1996, pp. 221-226.
      CCF to tear down the VC connection (LEG2)                  6)   Bretecher, Y., Vilain, B.: The Intelligent Net-
      between the CM video server and the sub-                        work in a Broadband Context. Proc. the XV
      scriber’s terminal. When the connection is                      International Switching Symposium, 2, 1995,
      torn down, the SCP is notified. A graphical                     pp. 57-61.
      representation of the CSM in this state is                 7)   Maastricht, C., Schalk, E.: Call Modeling in
      shown in Fig. 9 c).                                             a Broadband IN Architecture. Proc. the XV
                                                                      International Switching Symposium, 2, 1995,
                                                                      pp. 340-344.

FUJITSU Sci. Tech. J.,33,2,(December 1997)                                                                            125
M. Wakamoto et al.: Broadband Intelligent Network Architecture for Multimedia-on-Demand Service

                         Masaaki Wakamoto received the B.E.                                  Mitsunori Fukazawa received the B.E.
                         and M.E. degrees in Information Engi-                               and M.E. degrees in Information Sci-
                         neering from Yokohama National Uni-                                 ence from the Science University of
                         versity, Japan in 1980 and 1982, respec-                            Tokyo, Japan in 1983 and 1985, respec-
                         tively. He joined Fujitsu Laboratories                              tively. He joined Fujitsu Laboratories
                         Ltd., Kawasaki, Japan in 1982, where                                Ltd., Kawasaki, Japan in 1985, where
                         he has been engaged in research on                                  he has been engaged in research on
                         switching software CAD, an expert sys-                              switching software CAD, an expert sys-
                         tem for communications networks, and                                tem for communications networks, and
                         intelligent network architectures. He is                            intelligent network architectures. He is
                         a member of the IEEE, IEICE, and IPSJ.                              a member of the IEICE.

E-mail :                                  E-mail :

126                                                                                       FUJITSU Sci. Tech. J.,33,2,(December 1997)

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